The strengths and weaknesses of Vacuum Circuit Breaker technology

Vacuum switchgear is today the dominant technology worldwide for Medium Voltages up to 52kV, and is seen as the main candidate to replace SF6 circuit breakers at higher voltages. Vacuum switching technology was introduced into service in the late 1960's and since that time millions of vacuum circuit breakers have been manufactured. Today it is estimated that over a million vacuum circuit breakers will be manufactured worldwide annually. Vacuum circuit breaker technology now has been in large scale use for more than 40 years and has an enviable reputation for reliability in service. However amongst the very large numbers in service there are still occasional failures, and historically, particularly in the early days, there have been some problems due mainly to misapplication of the technology both by manufacturers and users. This paper examines the basics of Vacuum Circuit Breaker and particularly Vacuum Interrupter technology in order to identify their strengths and weaknesses. All technologies have their strengths and weaknesses and an understanding of what these are, and their effect on performance, permits the technology to be applied most effectively. The paper concludes that what are considered strengths and weaknesses of vacuum switchgear specific to the vacuum technology, particularly related to the vacuum interrupter, are in many cases the identical phenomena. The concept of strength or weakness being mainly related to the application or specific situation.